The invention relates to a fluid friction clutch having a driving element and a driven element which is rotatably supported on the driving element and which is entrained by the latter with fluid friction by means of a drive disk in a working space, and further having a locking device between the driving element and the driven element, as is known from DE-A 39 41 611.
This known locking device for a fluid friction clutch is relatively complicated from the points of view of manufacture, number of parts and, therefore, economy. The eccentric disks of this locking device, and the engagement surfaces corresponding to it, require certain tolerances in order to fulfil the required function reliably. This relatively high degree of manufacturing complexity is undesirable for such a mass-produced product, which is typically employed as a fan clutch in motor vehicles.
A further locking device is known from DE-U 91 03 493, in which a radial arm manufactured from sheet metal provides the drive for the clutch housing in the locked condition. Although this solution is relatively simple in a structural sense, it is less suitable for continuous operation, particularly in the case of large clutches.